In an LTE system, various downlink control information (DCI) is transmitted in a form of physical downlink control channel (PDCCH) by a base station, and data is transmitted in a form of physical downlink shared channel (PDSCH) by the base station. PDCCH and PDSCH are present in a time-division form in each subframe. As shown in FIG. 1, a first to an N-th OFDM (Orthogonal Frequency Division Multiplexing) symbols are possible transmission region of PDCCH, N=1, 2, 3 or 4, which is configured through a higher layer, and OFDM symbols starting from an (N+1)-th OFDM are transmission region of PDSCH. PDCCH supports spatial diversity multi-antenna transmission based on a cell-specific reference signal (CRS), with a maximum number of transmission antennas being 4. A region of PDCCH is further divided into a common search space and a UE-specific search space. Common search spaces of all user equipment (UE) are identical, and all UE searches PDCCH of its own in identical spaces. And the UE-specific search space is related to a radio network temporary identifier (RNTI) of the UE, in which the UE searches PDCCH of its own only. In searching PDCCH by UE, it is assumed that there are four possible aggregation levels, L=1, 2, 4, 8, and each aggregation level has multiple possible locations, referred to as multiple candidates. Location of each candidate may be calculated according to a predefined rule. As shown in Table 1, aggregation level of PDCCH corresponds to control channel element (CCE) one by one, a minimum aggregation level L=1 corresponding to one CCE, and one CCE corresponding to 36 resource elements (REs).
Number ofSearch space Sk(L)PDCCHAggregation levelcandidatesTypeLSize [in CCEs]M(L)UE-specific16621264828162Common41648162
In order to increase data transmission rate and to improve spectrum efficiency, multi-antenna has been widely used in wireless communication systems. In an LTE-advanced system, a downlink may support up to 8 transmission antennas, so as to reach a transmission rate of 1 Gbps. PDSCH may not only increase data transmission rate but also expand the coverage of a signal by precoding and beamforming. And PDCCH cannot support 8 antennas for transmission, and can only support a transmission diversity of up to 4 antennas, hence, it cannot obtain a beamforming gain identical to that of PDSCH. In order to further improve performance of cell-edge UE, a coordinated multipoint transmission technology based on a network architecture of multiple geographically separated remote radio heads (RRHs) shall be widely used in future wireless communication systems. In a network architecture of multiple RRHs, a cell split gain is obtained by simultaneously scheduling PDSCH of UE within a coverage of each RRH, so as to improve the cell capacity. And at the same time, the cell capacity may also be improved in a manner of space multiplexing of PDSCHs of multiple UE. As an existing CRS-based PDCCH cannot obtain a cell split gain, people start to pay attention to the study of a PDCCH based on a DM-RS (demodulation reference symbol), that is, the PDCCH is expanded from conventional former N OFDM symbols to a PDSCH region starting from an (N+1)-th OFDM symbol, as shown in FIG. 2. UE may obtain a location of a new PDCCH region through signaling, that is, information on a subcarrier resource occupied in a frequency domain and/or an OFDM symbol occupied in a time domain, and the UE may perform blind detection in such a region, so as to correctly demodulate a respective PDCCH.
In the implementation of the present invention, the inventors found that resource mapping of such new PDCCH is orientation of current studies.
It should be noted that the above description of the background art is merely provided for clear and complete explanation of the present invention and for easy understanding by those skilled in the art. And it should not be understood that the above technical solution is known to those skilled in the art as it is described in the background art of the present invention.